How To Build A Home Garden Koi Pond

This article originally appeared on the Jim's Exotic Fish website and dates back to 2006. I worked at the shop all throughout high school—my first job. Eventually I gave them a hand with their online marketing—my first customer. Sadly, Jim's shop has gone the way of the Megalodon, but this pond is still running.

One Summer day in 2006 I decided—rather ostentatiously—to dig up my parent’s backyard patio and teach myself how to make a koi pond. The process began innocently enough, I took a long hard look at the dilapidated corner of the patio that had been partially eaten away by an old fern in a half whiskey barrel, and decided that a hole filled with water and koi fish would be a much better use of that section of the yard.

Step 1. Dig a Hole

Once you’ve identified a suitable spot to make a koi pond (a partially shaded place where few leaves will fall ) outline the shape of your pond and start digging. If you are planning on making it larger than 5 feet in length and 3 feet in depth, you might need to rent a backhoe…but for an average sized koi pond a pick and a shovel will do just fine.

A good sized pond will be 5 feet long by 3 feet wide by 2 feet deep in the shallow end and 3-4 feet deep in the deep end. Be sure to give yourself a shallow end and a deep end, this will give your koi fish a shallow spot to eat, while still giving them plenty of deep swimming space to cruise around and hide from predators in. Fill the very bottom of the hole with 1-2 inches of peat gravel for drainage purposes.

Step 2. Shore up the Sides to Prevent a Cave-In

Because I dug my pond into a straight down “bath tub” shape, one of the biggest challenges I had when learning how to make a pond was figuring out how to hold back the earth from caving into my tub. Make a frame of your pond out of 4×8 wooden planks and place it into the hole.

Paint the frame with a water proof sealant to slow down the inevitable decay (after all, it is going to be underground) and make sure that it is level once it is in place and screwed together. Use stainless steel screws to join it all together and countersink them into the wood to prevent them from poking into the liner.

Step 3. Pad The Liner

I found that when making a koi pond, old strips of carpet make fantastic padding for the pond liner. Dig around a trash bin behind a carpet shop, or buy some remnant carpet pieces. It’s very wise to double (or triple) up on the padding under the liner, as it will also tend to break down over time, and you really want to minimize the amount of sharp objects that can put a hole in your pond liner one day and ruin the party.

Once your padding is down, you can throw your liner in. It’s a very uncomfortable time of day to do it, but try to lay your liner into the pond when the sun is high and at its hottest. The sun’s heat will loosen up the liner and make it more malleable and manageable, thus making your life much easier. Fold the liner onto itself where it overlaps, then go ahead and “fill er up” with freshwater from the garden hose. Do this slowly and pull and tug at the pond liner to get rid of any slack and wrinkles in the liner as you fill it with water.

The water will do most of the work, but be sure that the liner fits snugly into your frame without too much gap at the bottom corners of the tub. If you aren’t satisfied with the fit, you can always walk around and nudge the liner into place. Don’t worry…if you sufficiently padded the ground and frame you won’t poke any holes in your koi pond.

The hard work is done, now it’s time to set up your pond filters. Tetra Pond makes fantastic pond products that are relatively inexpensive and easy to install and maintain. If you have some experience in plumbing ponds or aquariums this should be pretty straightforward for you. Otherwise this might be the perfect time to go down to your local fish store and ask for some professional advice.